Naim NBL loudspeaker Measurements part 3

Vertically (fig.7), the tweeter's top octave gets hotter both above and below the tweeter axis, which is 34" from the floor, though a significant crossover-region suckout will be audible to standing listeners. But, as always, don't pass judgment on a speaker's balance unless you're sitting down.

The Naim's step response on the tweeter axis (fig.8) indicates that all of its drive-units are connected with positive acoustic polarity, although, unlike the Vandersteen 2Ce Signature (also reviewed in this issue), the Naim NBL is not time-coherent. Note that the output of the twin woofers (the rise starting at the 6.5ms mark) arrives about 1ms late to integrate smoothly with the tail end of the midrange unit's step. Though this usually correlates with less-than-optimum crossover integration, the NBL's boundary-adjacent mounting of the woofers makes it hard to predict what the overall effect will be.

Finally, the Naim's cumulative spectral-decay plot (fig.9) reveals some delayed energy present in the mid-treble, which might interfere with ultimate treble transparency and result in the "wearing" nature of high-level playback that PM noted.

Manufactured to a very high standard, and with heroic and successful efforts made to control cabinet resonances, the NBL's idiosyncratic measured performance strongly mandates careful auditioning.

One final note: It is not part of my usual brief to mention a speaker's documentation in this section, but the Naim's user's manual was so well-written, especially regarding the unpacking and setup of the speaker and the adjustment of the various suspensions, that I just had to let you know how highly I thought of it.—John Atkinson